The present invention relates to a method for assembling a motor-vehicle axle of the type comprising suspension arms carrying wheel supports, and a cross member mounted between the said suspension arms.
A motor-vehicle axle is generally equipped with two oscillating suspension arms, each carrying a wheel at one of their ends and which are articulated at their other end to the vehicle body. Elastic shock-absorbing means braced on the suspension arms support the body.
In the case of a motor-vehicle rear suspension, an axle additionally comprises a transverse bar that can be elastically deformed in torsion, rigidly connected via its ends to the two rear suspension arms.
The assembly of this cross member with the suspension arms not only must be particularly strong in order to efficiently transmit the forces undergone by the rear wheels of the vehicle to the body, but also must be constructed precisely in order to maintain the deflection of the axle during its spring movement.
In general, such assembly is achieved by press-fitting the cross member inside bores of the suspension arms, then welding these two elements to one another. More details can be found in the documents FR A3 2840854, WO A1 02/081239, US A1 2002/0005622, DE A1 19928537 and EP A1 0774369.
Such assemblies have the disadvantage that they do not withstand high induced stresses, thus making it particularly difficult to obtain axles comprising a cross member and suspension arms made with different materials, particularly with a view to reducing the total weight of the motor vehicle.
From document EP A2 0861744 there is known a motor-vehicle axle comprising suspension arms and a torsionally deformable transverse member constructed in the form of sections of design appropriate for being assembled merely by nesting.
In addition to the fact that the suspension arms and the cross member cause particularly laborious manufacture because of their design, the axle may have relatively poor operating reliability under conditions of large vibrations.
From document U.S. Pat. No. 6,389,697 there is also known a method for assembly of sections, in which method a first section is mounted in braced manner against a radial stop surface of a second section, in which there is machined an annular groove, then the first section is deformed radially by electromagnetic pulses so that its end becomes lodged in the interior of the said groove, and the sections are welded to one another.
Such an assembly method comprising steps of forming and electromagnetic welding has the disadvantage of consuming considerable energy.